Process for the electrochemical deposition of a semiconductor material

ABSTRACT

A process for the electrochemical deposition of a semiconductor material, which process comprises: (i) providing a non-aqueous solvent; (ii) providing at least one precursor salt which forms a source of the constituent elements within the semiconductor material to be deposited; and (iii) electrodepositing the semiconductor material onto an electrode substrate using the precursor salt in the non-aqueous solvent, characterised in that: (iv) the semiconductor material is a p-block or a post-transition metal semiconductor material containing at least one p-block element or post-transition metal; and (v) the non-aqueous solvent is a halocarbon non-aqueous solvent.

This invention relates to a process for the electrochemical depositionof a semiconductor material.

Processes for the electrodeposition of a semiconductor material are wellknown. It is also known that the electrodeposited semiconductor materialmay be used in the production of electronic devices. Phase change randomaccess memory devices are a strong contestant in the ongoing search forfaster, more compact, data storage devices. The phase change randomaccess memory devices are a potential competitor to flash drivescurrently in use. Semiconductor alloys containing bismuth and/orantimony with selenium and/or tellurium are important thermoelectricmaterials for harvesting low grade heat and the efficiency may beimproved significantly through nanostructuring. A problem occurs withknown processes in that it may not be possible to electrodeposit thesemiconductor material on a sufficiently small scale to enable desiredminiaturisation of phase change memory devices or thermoelectricsemiconductor materials.

It is an aim of the present invention to reduce the above mentionedproblem.

Accordingly, in one non-limiting embodiment of the present inventionthere is provided a process for the electrochemical deposition of asemiconductor material, which process comprises:

-   -   (i) providing a non-aqueous solvent;    -   (ii) providing at least one precursor salt which forms a source        of the constituent elements within the semiconductor material to        be deposited; and    -   (iii) electrodepositing the semiconductor material onto an        electrode substrate using the precursor salt in the non-aqueous        solvent,    -   characterised in that:    -   (iv) the semiconductor material is a p-block or a        post-transition metal semiconductor material containing at least        one p-block element or post-transition metal; and    -   (v) the non-aqueous solvent is a halocarbon non-aqueous solvent.

The process of the present invention is useful in the development andminiaturisation of memory storage devices, for example phase changememory storage devices. The process of the present invention may enablea distinct separation to be achieved between individual memory cells inphase change memory devices, for example, phase change random accessmemory devices. The separation of the individual memory cells may avoidcorruption during write/re-write processes. The memory storage devicesmay be used to provide fast and compact data storage, and thus thememory storage devices may compete with and replace existing flashdrives.

The process of the present invention may also be useful in theproduction of nanostructured thermoelectric devices or optical devices,for example waveguides and optical devices using optical metamaterials.

The process of the present invention may be one in which the halocarbonnon-aqueous solvent, is a fluoroalkane, a chloroalkane or a bromoalkane.

The halocarbon non-aqueous solvent may be a fluoro-, chloro- orbromo-alkane, including for example dichloromethane, chloroform,difluoromethane, trifluoromethane, 1,1-dichloroethane,1,2-dichloroethane, 1,1,1-trichloroethane or 1,1,2-trichloroethane. Thehalocarbon non-aqueous solvent may alternatively be a fluoro-, chloro-or bromo-benzene, for example, mono-, di- or tri-chlorobenzene, mono-,di- or tri-bromobenzene, or mono-, di- or tri-fluorobenzene. Thehalocarbon non-aqueous solvent may alternatively be a fluorotoluene, forexample, C₆H₅(CF₃) or C₆H₄(CF₃)₂, or o-, m- or p-fluorotoluene.

The precursor salt may be a halometallate anion salt. The halometallateanion may be a chlorometallate anion, a bromometallate anion, or aniodometallate anion.

The halometallate anion salt may have the general formula:

[cation]_(x)[M_(z)X_(y)]

-   -   where        -   x=1, 2 or 3        -   z=1 and then y=3, 4, 5 or 6        -   z=2 and then y=8, 9 or 10        -   M=Al, Ga, In, Ge, Sn, Pb, As, Sb, Bi, Se or Te and        -   X=Cl, Br or I

The above halometallate anion may be such that:

-   -   [M_(z)X_(y)]=        -   [AlX₄]⁻        -   [InX₄]⁻,        -   [GeX₅]⁻        -   [SbX₄]⁻        -   [BiX₄]⁻        -   [SbCl₆]⁻        -   [SeX₆]²⁻        -   [TeX₆]²⁻        -   [GaX₄]⁻        -   [GeX₆]²⁻        -   [GeX₃]⁻        -   [SnX₆]⁻        -   [SnX₅]⁻        -   [SnX₃]⁻        -   [PbX₃]⁻        -   [PbX₆]²⁻        -   [AsX₄]⁻        -   [SbX₅]²⁻        -   [SbX₆]³⁻        -   [BiX₅]²⁻        -   [BiX₆]³⁻        -   [Sb₂X₈]²⁻        -   [Bi₂X₈]²⁻        -   [Se₂X₁₀]²⁻        -   [Te₂X₁₀]²⁻        -   [CdX₄]²⁻        -   [CdX₅]³⁻        -   [HgX₄]²⁻        -   [HgX₅]²⁻        -   [HgX₃]⁻

The precursor salt may be one in which the cation in the precursor saltcontains a redox inactive cation. The redox inactive cation may be aquaternary ammonium cation having a group [R₄N]⁺ where R=alkyl. In thiscase, R may be methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl,cyclopentyl, cyclohexyl, or mixtures thereof.

Alternatively, the precursor salt may be one in which the redox inactivecation in the precursor salt is imidazolium; alkyl substitutedimidazolium, where alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl,benzyl, cyclopentyl, cyclohexyl, or mixtures thereof; pyrrolidinium;alkyl substituted pyrrolidinium where alkyl is methyl, ethyl, propyl,butyl, pentyl, hexyl, benzyl, cyclopentyl, cyclohexyl, or mixturesthereof; [PPh₄]⁺; [AsPh₄]⁺ or [(PPh₃)₂N]⁺.

Preferably, the process of the present invention includes providing asupporting electrolyte salt for the non-aqueous solvent. However, if thesolubility of the precursor salt is high enough, then the process of thepresent invention may be conducted without the supporting electrolytesalt. The supporting electrolyte salt may be used to maintain therequired conductivity in the electrochemical solution.

Preferably, the supporting electrolyte salt is a redox inactive salt.The redox inactive salt may be in the form of a cation and an anion.

The anion in the supporting electrolyte salt may be a halide,tetrafluoroborate, hexafluorophosphate, a tetra-arylborate, afluorinated tetra-aryl borate, tetra-alkoxyaluminate, or a fluorinatedtetra-alkoxyaluminate.

The cation in the supporting electrolyte salt may be a redox inactivequaternary ammonium cation salt having a group [R₄N]⁺ where R=alkyl. Thealkyl may be methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl,cyclopentyl, cyclohexyl, or mixtures thereof.

The process may be one in which the electrodeposition is a continuouselectrodeposition. Alternatively, the electrodeposition may be a pulsedelectrodeposition.

The semiconductor material may be electrodeposited as at least oneshaped structure. The shaped structure may be a pillar, a waveguide, aring, a spherical particle, or a flat formation. Other shaped structuresmay be electrodeposited on differently shaped electrode substrates.

The process of the present invention may be one in which the electrodesubstrate is an electrode substrate having insulating pores, in whichthe shaped structure is a plurality of pillars, and in which the pillarsare electrodeposited in the insulating pores.

Alternatively, the process of the present invention may be one in whichthe semiconductor material is electrodeposited all over the electrodesubstrate, the electrode substrate being a flat electrode substrate.

The semiconductor material is preferably a compound semiconductorcontaining two or more p-block elements. Other semiconductor materialsmay however be employed so that, for example, the semiconductor materialmay be a single semiconductor element or a semiconductor alloy.

Examples of suitable p-block elements may include gallium, indium,silicon, germanium, phosphorus, arsenic, antimony, bismuth, selenium ortellurium. Example of suitable post-transition metals may includecadmium or mercury. Within the Examples described below, the binarysemiconductor indium antimonide is useful as an infrared detector, whileantimony telluride is useful both as a phase change memory material andalso as a thermoelectric material. The ternary germanium antimonytelluride is an important phase change memory material.

In order to facilitate a full and complete understanding of the processof the present invention, reference will now be made, solely for thepurposes of illustration, to the following Examples.

In the following Examples 1-16, there is described the electrodepositionof several individual p-block elements from Groups 13, 14 and 15 of theperiodic table, binary semiconductor materials onto flat and patternedelectrode substrates and ternary semiconductor materials. The Examplesalso show that the composition of the alloys, purity levels, morphologyand density can be optimised using the system described.

EXAMPLE 1

Electrodeposition of an indium antimonide (InSb) semiconductor material.

This Example describes the electrodeposition of an indium antimonidesemiconductor material from a solution composed of 10 mM[^(n)Bu₄N][InCl₄], 2 mM [^(n)Bu₄N][SbCl₄] and 100 mM ^(n)Bu₄NCl indichloromethane. The [^(n)Bu₄N][InCl₄] and [^(n)Bu₄N][SbCl₄] are twoprecursor salts which are used in tandem. The ^(n)Bu₄NCl is a supportingelectrolyte salt.

The electrochemical system was set up in a glove box to exclude moistureand oxygen contamination. A TIN coated silicon chip was used as theworking electrode, i.e. the electrode substrate. The TIN coated siliconchip was sputtered with SiO₂ (except for a 4 mm diameter circle as anelectrode area and a 5 mm² square as a contact area) to form a substratewith a well-defined conducting TiN electrode area. A Pt gauze was usedas a counter electrode. An AgCl coated Ag wire immersed in a 100 mMsolution of ^(n)Bu₄NCl in dichloromethane was used as the referenceelectrode (denoted Ag/AgCl, 0.1 M Cl⁻, CH₂Cl₂).

In order to determine the ideal conditions for the electrodeposition,cyclic voltammetry was performed on the electrochemical solution using aTiN electrode. The potential scan rate was 50 mV s⁻¹. The depositionpotential was subsequently set to −1.2 V vs. Ag/AgCl (0.1 M Cl⁻,CH₂Cl₂), where a peak was observed in the voltammogram.

Deposition times of less than 100 seconds led to pure, crystalline InSb.

This formed as a fine dark grey deposit of the semiconductor material onthe electrode substrate. Characterisation by scanning electronmicroscopy showed that the electrodeposited semiconductor material wasuniform and grainy, with grain sizes of several hundred nanometres.Energy dispersive X-ray measurements showed that the deposited materialconsisted of InSb with an elemental ratio of 1.02 In:1 Sb.

EXAMPLE 2 Electrodeposition of an Antimony Telluride SemiconductorMaterial onto a Flat TiN Electrode

Antimony telluride was deposited onto flat TiN electrodes from asolution containing 10 mM [^(n)Bu₄N][SbCl₄], 10 mM [^(n)Bu₄N]₂[TeCl₆]and 100 mM ^(n)Bu₄NCl in dichloromethane solution.

The electrochemical set-up was as described in Example 1.

As for Example 1, the deposition potential was determined by recording acyclic voltammogram at 50 mV s⁻¹ on the electrochemical solution using aTiN coated silicon chip as the electrode. Electrodeposition wassubsequently performed on a fresh electrode at −1.5 V vs Ag/AgCl (0.1 MCl⁻, CH₂Cl₂) for 1800 seconds.

Antimony telluride formed as a thick grey-black flaky deposit on theelectrode substrate. Scanning electron microscopy showed that thissemiconductor material was composed of grains with diameters rangingfrom hundreds of nanometres to a few micrometres. Characterisation byenergy dispersive X-ray measurements suggested that this depositedsemiconductor material had a SbTe₃ stoichiometry. X-Ray diffractionanalysis revealed that the obtained material was predominantlyamorphous.

EXAMPLE 3 Improving the Composition of the Antimony TellurideSemiconductor Material by Varying the Electrolyte Composition

A SbTe composition of Sb₁Te₁ was identified as an initial targetmaterial. In order to achieve this, the electrolyte from Example 2 wasmodified. The electrolyte was prepared from 10 mM [^(n)Bu₄][SbCl₄], 5 mMand [^(n)Bu₄N]₂[TeCl₆] in 0.1 M [^(n)Bu₄N]Cl in dichloromethane. Thiselectrolyte composition resulted in a stoichiometric amorphous SbTecompound at a deposition potential of −0.5 V vs Ag/AgCl (0.1 M Cl⁻,CH₂Cl₂). The 1:1 Sb:Te ratio was confirmed by energy dispersive X-rayanalysis. The stoichiometry of the SbTe compound could be controlled bychanging the deposition potential.

EXAMPLE 4 Improving the Morphology of the Antimony TellurideSemiconductor Material by Varying the Deposition Potential Waveform

The composition of the SbTe compound was predominantly controlledthrough the electrolyte composition as described in Example 3. Themorphology of the antimony telluride was controlled through theelectrodeposition waveform. Instead of only applying a constantelectrodeposition potential as described in Example 3, this potentialwas preceded by a nucleation step, where the electrode was held at −1.5V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 100 ms before it was switched to−0.5 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) where the film was grown. Thenucleation step allowed the formation of a layer of dense nuclei whichwere subsequently grown into films consisting of hundreds ofnanometre-sized particles with a Sb₁Te_(0.8) composition.

EXAMPLE 5 Electrodeposition of an Antimony Telluride SemiconductorMaterial onto a Patterned TiN Electrode

The semiconductor material antimony telluride was electrodeposited ontoa micropatterned TiN coated silicon wafer electrode, as described inExample 10, from an electrochemical solution containing 10 mM[^(n)Bu₄N][SbCl₄], 10 mM [^(n)Bu₄N]₂[TeCl₆] and 100 mM ^(n)Bu₄NCl indichloromethane.

The electrochemical system was as described in Example 1.

As described in Example 1, the electrodeposition potential wasdetermined by recording a cyclic voltammogram with a TiN coated siliconwafer electrode. Electrodeposition was subsequently performed on thesame electrode at −1.5 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 900 seconds.

Scanning electron microscopy images showed that the antimony telluridesemiconductor material had deposited into holes with diameters rangingfor 100 μm down to 1 μm. The deposit only formed inside the holes on theconducting TiN surface, and not on the SiO₂ coated regions of thepatterned electrode. Further down scaling is expected to be possible.

The adhesion between the electrodeposited antimony telluridesemiconductor material and the TiN substrate is not very strong,allowing easy removal of individual pillars. A scanning electronmicrograph of an individual pillar of the antimony telluridesemiconductor material was taken.

Energy dispersive X-ray spectra of a larger area of electrodepositedantimony telluride semiconductor material suggested a similarcomposition to the one obtained in Example 2. The stoichiometry of thiselectrodeposited semiconductor material is SbTe₃.

EXAMPLE 6 Improving the Electrodeposition of an Antimony TellurideSemiconductor Material onto a Patterned TiN Electrode Using AdjustedElectrolyte Concentrations and Deposition Potential Waveforms

The antimony telluride semiconductor material was electrodeposited ontoa micropatterned TiN coated silicon wafer electrode, as described inExample 10, from an electrochemical solution containing 10 mM[^(n)Bu₄N][SbCl₄], 5 mM [^(n)Bu₄N]₂[TeCl₆] and 100 mM ^(n)Bu₄NCl indichloromethane.

The electrochemical set-up was as described in Example 1.

As described in Example 4, the electrodeposition was preceded by anucleation step where the electrode was held at −1.5 V vs Ag/AgCl (0.1 MCl⁻, CH₂Cl₂) for 250 ms. Subsequently, the semiconductor material wasgrown at 0.5 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 75 s.

Scanning electron microscopy images showed that the antimony telluridesemiconductor material had deposited into holes with diameters rangingfor 100 μm down to 2 μm. The deposit only formed inside the holes on theconducting TiN surface, and not on the SiO₂ coated regions of thepatterned electrode. Further down-scaling is expected to be possible.

Energy dispersive X-ray spectra of the electrodeposited antimonytelluride semiconductor material suggested a similar composition to theone obtained in Example 4. The stoichiometry of this electrodepositedsemiconductor material is approximately Sb₁Te_(0.7).

Microfocus X-ray diffraction measurements were performed on Beamline 118at the Diamond Light Source, Didcot, Oxfordshire, UK, using X-rays ofwavelength 0.738 Å with beam dimension of 2×4 μm and collected using a4000×2500 pixel CCD detector. Transmission measurements were performedthrough the substrate; background measurements were subtracted aftercollection on similar areas of substrate lacking deposited material. Themicrofocus X-ray diffraction measurements confirmed the presence ofcrystalline SbTe inside pores with diameters of down to 5 μm afterannealing at 160° C. for 15 minutes.

EXAMPLE 7

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofelemental indium, or of an indium-containing semiconductor material asdescribed in Example 1.

[^(n)Bu₄N][InCl₄]: The preparation of this precursor salt was describedin Inorg. Chem., 1971, 10, 1907. A Schlenk tube was loaded with InCl₃(0.447 g, 2.02×10⁻³ mol) and ^(n)Bu₄NCl (0.559 g, 2.01×10⁻³ mol). Withstirring, CH₃CN (30 mL) was added, giving a clear, colourless solution.After stirring at room temperature for approximately one hour, thesolution was concentrated in vacuo to ca. 8 mL, layered with diethylether (40 mL) and stored at ca. −18° C. A large mass of colourlesscrystals formed overnight, and these were collected by filtration,washed with diethyl ether and dried in vacuo. Yield: 0.628 g, 63%. Anal.Calcd. for C₁₆H₃₆Cl₄InN: C, 38.5; H, 7.3; N, 2.8. Found: C, 38.4; H,7.5; N, 2.9%. ¹¹⁵In NMR (CH₃CN/CD₃CN, 298 K): 451; (+ca. 1 mol. equiv.[^(n)Bu₄N]Cl): 318; (+ca. 10 mol. equiv. [^(n)Bu₄N]Cl): 251. IR(Nujol/cm⁻¹): 331. Raman (cm⁻¹): 326, 335.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N][InCl₄] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at −1V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 3600 s on glassy carbon and at −1.3V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 3600 s on TiN. Scanning electronmicroscopy energy dispersive X-ray spectra and X-ray diffraction dataconfirmed the preparation of a pure indium film.

EXAMPLE 8

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofantimony, or of metal antimonide semiconductor material as described inExample 1.

[^(n)Bu₄N][SbCl₄]: The preparation of this precursor salt was describedin Red Trav. Chim. Pays-Bas, 1970, 89, 1297. A Schlenk tube was loadedwith SbCl₃ (0.461 g, 2.02×10⁻³ mol) and ^(n)Bu₄NCl (0.559 g, 2.01×10⁻³mol). With stirring, CH₂Cl₂ (20 mL) was added, giving a clear,colourless solution. After stirring at room temperature for 30 min., thesolution was concentrated in vacuo to ca. 10 mL, layered with hexane (20mL) and stored at ca. −18° C. A large mass of colourless crystalsappeared overnight. These were collected by filtration, washed withhexane and dried in vacuo. Yield: 0.977 g, 96%. Anal. Calcd. forC₁₆H₃₆Cl₄NSb: C, 38.0; H, 7.2; N, 2.8. Found: C, 38.0; H, 7.5; N, 2.8%.IR (Nujol/cm⁻¹): 269, 345. Raman (cm⁻¹): 254, 288, 345.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N][SbCl₄] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at−0.75 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on glassy carbon andat −1.2 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on TiN. Scanningelectron microscopy energy dispersive X-ray spectra and X-raydiffraction data confirmed the preparation of a pure antimony film.

EXAMPLE 9

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition oftellurium, or of a metal telluride semiconductor material as describedin Example 2 and Example 3.

[^(n)Bu₄N]₂[TeCl₆]: The preparation of this precursor salt was asdescribed in J. Am. Chem. Soc., 1970, 92, 307. A Schlenk tube was loadedwith TeCl₄ (0.269 g, 9.98×10⁻⁴ mol) and ^(n)Bu₄NCl (0.559 g, 2.01×10⁻³mol). With stirring, CH₂Cl₂ (40 mL) was added, giving a cloudy yellowsolution. This was stirred at room temperature for ca. 1 hour, and thenfiltered. The clear yellow filtrate was concentrated in vacuo to ca. 5mL, layered with diethyl ether (10 mL) and stored at ca. −18° C. A solidyellow mass formed overnight, which was collected by filtration, washedwith diethyl ether and dried in vacuo. Yield: 0.694 g, 84%. Anal. Calcd.for C₃₂H₇₂Cl₆N₂Te:C, 46.6; H, 8.8; N, 3.4. Found: C, 46.4; H, 8.7; N,3.5%. ¹²⁵Te{¹H} NMR (CH₂Cl₂/CD₂Cl₂, 298 K): 1324. IR (Nujol/cm⁻¹): 223.Raman (cm⁻¹): 242, 283.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N]₂[TeCl₆] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at−0.4 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on glassy carbon and at−0.8 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on TiN. Scanningelectron microscopy energy dispersive X-ray spectra and X-raydiffraction data confirmed the preparation of a pure tellurium film.

EXAMPLE 10 Patterned Electrode Preparation

This Example describes the preparation of the patterned TiN/SiO₂electrodes onto which the semiconductor materials were electrodeposited.TiN films with a thickness of 100 nm were deposited on a p-type Si (100)wafer by the medium frequency magnetron sputtering method at roomtemperature (type: Leybold HELIOS Pro). The films were deposited under aTi (99.99% purity) target with a DC power of 3000 W in a N₂/Aratmosphere. The N₂ and Ar flow rates were maintained at 30 and 35 sccm,respectively. A high drive speed of 180 rpm was applied to enhance thefilm uniformity. The deposition rate was found to be 0.161 nm s⁻¹. SiO₂films with a thickness of 1 μm were also formed by the medium frequencymagnetron sputtering method using a pure Si (99.99% purity) target witha DC power of 2000 W in an O₂/Ar atmosphere. The O₂ and Ar flow rateswere maintained at 20 sccm and 40 sccm, respectively. With the samedrive speed of 180 rpm, the deposition rate was 0.3 nm s⁻¹. Thepatterned samples were fabricated via a photolithographic processfollowed by reactive-ion etching of SiO₂. The pattern was pre-designedon a mask with template hole-sizes ranging from 1 μm to 100 μm. Thephotolithography was carried out using an EVG 620 TB with a positiveresist S1813. The etching was performed by a RIE80+ with CHF₃ and Ar.The etching rate was found to be 22 nm s⁻¹.

EXAMPLE 11

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofelemental bismuth.

[^(n)Bu₄N][BiCl₄]: The preparation of this precursor salt was asdescribed in Chem. Commun., 1968, 1356-1358 and J. Chem. Soc. A, 1970,326-329. A Schlenk tube was loaded with BiCl₃ (0.319 g, 1.01×10⁻³ mol)and [^(n)Bu₄N]Cl (0.280 g, 1.01×10⁻³ mol). With stirring, CH₃CN (20 mL)was added, giving a colourless solution. After stirring at roomtemperature for approximately 2 hours, the mixture was concentrated invacuo to ca. 5 mL, layered with diethyl ether and stored at ca. ˜18° C.A colourless, microcrystalline solid formed over a period of a few days.This was collected by filtration, washed with diethyl ether and dried invacuo. Yield: 0.403 g (68%). Anal. Calcd. for C₁₆H₃₆BiCl₄N: C, 32.3; H,6.1; N, 2.4. Found: C, 33.1; H, 6.0; N, 2.5%. IR (Nujol/cm⁻¹): 256, 287.Raman (cm⁻¹): 254, 289.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N][BiCl₄] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at−0.59 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on glassy carbon andat −0.97 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s on TiN. Scanningelectron microscopy energy dispersive X-ray spectra and X-raydiffraction data confirmed the preparation of a pure bismuth film.

EXAMPLE 12

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofelemental selenium.

[^(n)Bu₄N]₂[SeCl₆]: A Schlenk tube was loaded with SeCl₄ (0.219 g,9.92×10⁻⁴ mol) and [^(n)Bu₄N]Cl (0.556 g, 2.00×10⁻³ mol). With stirring,tetrahydrofuran (20 mL) was added, giving an almost clear yellowsolution which rapidly deposited a large amount of a light yellow solid.This was collected by filtration, washed with a small amount oftetrahydrofuran and dried in vacuo. Yield: 0.610 g (79%). Anal. Calcd.for C₃₂H₇₂Cl₆N₂Se: C, 49.5; H, 9.4; N, 3.6. Found: C, 49.7; H, 9.8; N,3.7%. ⁷⁷Se NMR (CH₂Cl₂/CD₂Cl₂, 298 K): 5=881. Raman (cm⁻¹): 236, 284.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N]₂[SeCl₆] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at −1V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 57600 s on glassy carbon and at −1V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 3600 s on TiN. Scanning electronmicroscopy energy dispersive X-ray spectra and X-ray diffraction dataconfirmed the preparation of a pure selenium film.

EXAMPLE 13

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofgermanium to produce alloys including germanium antimony telluride.

[^(n)Bu₄N][GeCl₅]: The preparation of this precursor salt was asdescribed in J. Chem. Soc. (A), 1967, 712-718. GeCl₄ (0.295 g, 1.38×10³mol) and [^(n)Bu₄N]Cl (0.381 g, 1.37×10³ mol) were loaded into a Schlenktube. CH₂Cl₂ (20 cm³) was added, giving a clear, colourless solution.This was stirred magnetically at room temperature for one hour, and thenthe solution was concentrated in vacuo to approximately half of theoriginal volume and layered with diethyl ether (40 cm³). The mixture wasstored at ca. −18° C., and large colourless crystals appeared over aperiod of two days. These were collected by filtration, washed withdiethyl ether (20 cm³) and dried in vacuo. Yield: 0.486 g, 72%. Anal.Calc. for C₁₆H₃₆NCl₅Ge (%): C, 39.03; H, 7.37; N, 2.84%. Found: C,38.02; H, 7.29; N, 2.88. Raman (cm⁻¹): 238 (w), 349 (s), 405 (vw).

EXAMPLE 14

This Example describes the preparation and characterisation of one ofthe halometallate precursor salts used for the electrodeposition ofelemental germanium.

[^(n)Bu₄N][GeCl₃]: The preparation of this precursor salt was analogousto that described for [NEt₄][GeCl₃] described in Inorg. Synth., 1974,15, 222-225, by reaction of GeCl₄, H₃PO₂ and [^(n)Bu₄N]Cl in aqueousHCl. The crude product was recrystallised from ethanol and dried for aprolonged period in vacuo. Yield: 60%. Anal. Calc. for C₁₆H₃₆NCl₃Ge (%):C, 45.48; H, 8.61; N, 3.32. Found: C, 45.47; H, 8.70; N, 3.35%. IR(Nujol/cm⁻¹): 270, 326.

The suitability of the compound for electrodeposition was tested byrecording cyclic voltammograms on glassy carbon and TiN electrodes. Theelectrochemical set-up was as described in Example 1. The electrolytewas prepared from 10 mM [^(n)Bu₄N][GeCl₃] and 0.1 M [^(n)Bu₄N]Cl indichloromethane. The electrodeposition was subsequently performed at−1.4 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 3600 s on glassy carbon and at−1.4 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 7200 s on TiN. On bothelectrode materials the deposition was self-limiting and film growthstopped after approximately 10 minutes. Analysis of the Ge film byscanning electron microscopy, energy dispersive X-ray spectra and X-raydiffraction data after annealing in N₂ at 600° C. for 45 mins. confirmedthe preparation of a germanium film.

EXAMPLE 15 Electrodeposition of a Germanium Antimony Telluride TernarySemiconductor Material onto a Flat TiN Electrode

A ternary germanium antimony telluride, GeSbTe, phase changesemiconductor material was prepared by electrodeposition using the sameapproach as described in Example 3. The electrolyte was prepared from 10mM [^(n)Bu₄N][GeCl₅], 10 mM [^(n)Bu₄N][SbCl₄], 5 mM [^(n)Bu₄N]₂[TeCl₆]and 0.1 M [^(n)Bu₄N]Cl in dichloromethane. The electrodepositionconditions were evaluated from cyclic voltammograms and a range ofdeposition potentials were evaluated to obtain a variety of differentGeSbTe stoichiometries. The as-deposited material was formed ashomogeneous amorphous films made from spherical particles with diametersof less than a micrometre.

EXAMPLE 16 Electrodeposition of a Germanium Antimony Telluride TernarySemiconductor Material onto a Patterned TiN Electrode

A ternary germanium antimony telluride, GeSbTe, phase changesemiconductor material was also formed within micropatterned electrodesubstrates. The same deposition conditions as described in Example 15were used.

Scanning electron microscopy and energy dispersive X-ray analysissuggested the films were made from the ternary compound.

X-ray diffraction before and after annealing also supported theformation of crystalline germanium antimony telluride.

In order to further illustrate the present invention, reference will nowbe made to the following drawings in which:

FIG. 1 shows a cyclic voltammogram recorded on a TiN electrode of theelectrochemical solution containing the precursor salts and supportingelectrolyte dissolved in CH₂Cl₂ for the InSb electrodeposition,corresponding to Example 1;

FIG. 2 shows a chronoamperometric curve recorded on a TiN electrode ofthe electrochemical solution containing the precursor salts andsupporting electrolyte salt dissolved in CH₂Cl₂ for the InSbelectrodeposition corresponding to Example 1;

FIG. 3 shows a 2000× magnification of the electrodeposited InSbsemiconductor material described in Example 1;

FIG. 4 shows a magnified section of the energy dispersive X-ray spectrumof the InSb semiconductor material corresponding to Example 1;

FIG. 5 shows a Raman spectrum of the InSb semiconductor materialdeposited corresponding to Example 1;

FIG. 6 shows an X-ray diffraction pattern of the semiconductor materialdescribed in Example 1;

FIG. 7 shows a cyclic voltammogram recorded on a TiN electrode from theelectrochemical solution containing the precursor salts and supportingelectrolyte salt dissolved in CH₂Cl₂ for the antimony tellurideelectrodeposited according to the description in Example 2;

FIG. 8 shows a chronoamperometric curve recorded on a TiN electrode ofthe electrochemical solution containing the precursor salts andsupporting electrolyte salt dissolved in CH₂Cl₂ for the antimonytelluride electrodeposited according to the description in Example 2;

FIG. 9 shows a 2000× magnification of the electrodeposited antimonytelluride semiconductor material described in Example 2;

FIG. 10 shows the energy dispersive X-ray spectrum of theelectrodeposited antimony telluride semiconductor material shown in FIG.9, and corresponding to Example 2;

FIG. 11 shows a cyclic voltammogram recorded on a TIN electrode from theelectrochemical solution containing the precursor salts and supportingelectrolyte salt dissolved in CH₂Cl₂ for the electrodeposition ofantimony telluride as described in Example 3;

FIG. 12 shows a chronoamperometric curve recorded on a TiN electrode ofthe electrochemical solution containing the precursor salts andsupporting electrolyte salt dissolved in CH₂Cl₂ for the antimonytelluride electrodeposition as described in Example 3;

FIG. 13 shows a 2000× magnification of the electrodeposited antimonytelluride semiconductor material described in Example 3;

FIG. 14 shows the potential-dependent Sb:Te ratio determined by energydispersive X-ray analysis for the antimony telluride electrodeposited asdescribed in Example 3;

FIG. 15 shows the cyclic voltammogram of the electrochemical solutioncontaining the precursor salts and supporting electrolyte salt dissolvedin CH₂Cl₂ for the antimony telluride electrodeposition as described inExample 4;

FIG. 16 shows a chronoamperometric curve of the electrochemical solutioncontaining the precursor salts and supporting electrolyte salt dissolvedin CH₂Cl₂ for the antimony telluride electrodeposition as described inExample 4;

FIG. 17 shows a scanning electron micrograph of a 10000× magnificationof an area of the antimony telluride electrodeposited onto TiN asdescribed in Example 4;

FIG. 18 shows the energy dispersive X-ray spectrum of the antimonytelluride electrodeposited as described in Example 4 and shown in FIG.17;

FIG. 19 shows the X-ray diffraction pattern of the antimony tellurideelectrodeposited as described in Example 4, (a) before and (b) afterannealing at 250° C.;

FIG. 20 shows a 125× magnification of an area of the patterned TINelectrode with hole sizes between 10 and 1 μm containing antimonytelluride deposited as described in Example 5;

FIG. 21 shows the energy dispersive X-ray spectrum corresponding to theantimony telluride semiconductor material deposited as described inExample 5;

FIG. 22 shows the scanning electron micrograph of the antimony telluridesemiconductor material deposited into 1 to 100 micron diameter holes asdescribed in Example 6;

FIG. 23 shows the energy dispersive X-ray analysis scanning of theantimony telluride semiconductor material deposited into 1-10 microndiameter holes as described in Example 6;

FIG. 24 shows the microfocus X-ray diffraction pattern for the antimonytelluride semiconductor material deposited into 100 micron diameterholes as described in Example 6, after annealing at 160° C. for 15 min;a background spectrum was subtracted and the spectrum was shifted by2θ=1°;

FIG. 25 shows the cyclic voltammograms for the electrochemical solutionsdescribed in Examples 7, 8, 9, 11 and 12 using (a) glassy carbon (GC)and (b) TiN electrodes;

FIG. 26 shows the scanning electron micrographs from the elementalindium, antimony, tellurium, bismuth and selenium electrodeposited onTiN electrodes using the reagents and electrochemical conditions asdescribed in Examples 7, 8, 9, 11 and 12;

FIG. 27 shows the energy dispersive X-ray analyses from the elementalindium, antimony, tellurium, bismuth and selenium electrodeposited onTiN electrodes using the reagents and electrochemical conditions asdescribed in Examples 7, 8, 9, 11 and 12;

FIG. 28 shows the X-ray diffraction patterns from the elemental indium,antimony, tellurium, bismuth and selenium electrodeposited on TiNelectrodes using the reagents and electrochemical conditions asdescribed in Examples 7, 8, 9, 11 and 12;

FIG. 29 shows the cyclic voltammogram from the electrochemical solutioncontaining the precursor salt described in Example 14 and the supportingelectrolyte salt dissolved in CH₂Cl₂ and using a glassy carbon workingelectrode;

FIG. 30 shows the scanning electron micrograph at 2000× magnification ofthe elemental germanium electrodeposited on TiN at −1.4 V vs Ag/AgCl(0.1 M Cl⁻, CH₂Cl₂) for 7200 s using the reagent described in Example14;

FIG. 31 shows energy dispersive X-ray analysis of the elementalgermanium electrodeposited on TiN using the reagent described in Example14 and after annealing at 600° C. for 2 hours;

FIG. 32 shows an X-ray diffraction pattern obtained from the elementalgermanium electrodeposited on TiN using the reagent described in Example14 and after annealing at 600° C. for 2 hours;

FIG. 33 shows the cyclic voltammogram from the electrochemical solutioncontaining the precursor salts and supporting electrolyte dissolved inCH₂Cl₂ using a TiN working electrode for electrodeposition of a ternarygermanium antimony telluride semiconductor material as described inExample 15;

FIG. 34 shows the scanning electron micrograph of the ternary germaniumantimony telluride semiconductor material electrodeposited at −1.75 V vsAg/AgCl (0.1 M CH₂Cl₂) for 120 s as described in Example 15;

FIG. 35 shows the energy dispersive X-ray analysis of the ternarygermanium antimony telluride semiconductor material electrodepositedshown in FIG. 32 as described in Example 15;

FIG. 36 shows the X-ray diffraction pattern of the ternary germaniumantimony telluride semiconductor material electrodeposited shown inFIGS. 34 and 35 as described in Example 15 after annealing at 250° C.for 30 min; and

FIG. 37 shows the scanning electron micrograph of the ternary germaniumantimony telluride semiconductor material electrodeposited into poreswith 1-3 μm diameter as described in Example 16.

Referring to the drawings, FIG. 1 shows that the electrochemicalsolution for the deposition of indium antimonide semiconductor materialdescribed in Example 1 has its reduction peak at −1.2 V vs Ag/AgCl (0.1M CH₂Cl₂). On this basis, the chromoamperometry for this system, shownin FIG. 2, was also performed at −1.2 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂)for 100 s, allowing significant charge to pass.

In FIG. 3, a homogeneous film with grains of a few 100 nm is visible onthe electrode, and FIG. 4 shows that this electrodeposited materialcontains both In and Sb, in addition to the peaks for Si, Ti and N whichare due to the electrode substrate. It also shows that the Cl content ofthe film is low.

The Raman spectrum shown in FIG. 5 is consistent with theelectrodeposited material formed as described in Example 1 being indiumantimonide, InSb. This is strong evidence that combining two of thehalometallate reagents does allow electrodeposition of a binarysemiconductor material, Further, referring to FIG. 6, the X-raydiffraction pattern of the material shows peaks consistent withcrystalline InSb, as well as peaks from the TiN substrate.

Referring to FIG. 7, the electrochemical solution described in Example 2shows an ill-defined reduction at around −1.5 V vs Ag/AgCl (0.1 M Cl⁻,CH₂Cl₂). As shown in FIG. 8, the chronoamperometry was then performed at−1.5 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 1800 s, and the scanningelectron micrograph shown in FIG. 9 shows that the electrodepositedmaterial generally covers the electrode well, although its morphology israther ill-defined with irregular grain sizes. Referring to FIG. 10, itcan be seen that the electrodeposited material formed as described inExample 2 contains both Sb and Te, suggesting that both elements areco-deposited in the process described in Example 2. Peaks from theelectrode substrate are also evident, as well as Cl and C, probablyarising from supporting electrolyte, [^(n)Bu₄N]Cl, trapped in the quitelow density (highly porous) deposit.

FIG. 11 shows the cyclic voltammogram measured on a TiN electrolyte fromthe electrochemical solution used to deposit the antimony telluride inwhich the relative concentrations of the two halometallate salts wereadjusted in order to achieve a 1:1 ratio of antimony:tellurium in theelectrodeposited material, as described in Example 3. Thechronoamperogram for this modified electrolyte solution is shown in FIG.12. Referring to FIG. 13, it can be seen from the scanning electronmicrograph that the antimony telluride material electrodeposited formsquite isolated globular particles on the electrode surface using theelectrodeposition conditions as described in Example 3.

Varying the relative concentrations of the antimony and indiumhalometallate salts as described in Example 3, allows the composition ofthe electrodeposited antimony telluride material to be varied as shownin FIG. 14. However, it is desirable to be able to control themorphology of the electrodeposited semiconductor material for certainapplications.

In Example 4 the concentrations of the halometallate salts in theelectrochemical system were fixed. The cyclic voltammogram andchronoamperometry of this solution are shown in FIGS. 15 and 16respectively. Then, in order to improve the morphology of thesemiconductor material, electrodeposition was carried out by firstapplying a nucleation pulse step, where the electrode was held at −1.5 Vvs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂) for 100 ms, before it was switched to−0.5 V vs Ag/AgCl (0.1 M Cl⁻, CH₂Cl₂), where the film was grown. Thenucleation step allowed the formation of a layer of dense nuclei whichwere subsequently grown into films consisting of hundreds ofnanometre-sized particles as shown in FIG. 17, where it can also be seenthat the coverage of the electrode is much higher. FIG. 18 shows thatthis material contains antimony and tellurium.

In FIG. 19 it can be seen that the electrodeposited antimony telluridecan be crystallised by annealing the sample under N₂ at 250° C. Thediffraction peaks present before annealing correspond to the TiNelectrode, with some additional broad features evident. The lattersharpen on annealing, consistent with crystallisation, as thediffraction pattern resulting from these new peaks correspond to thepattern for antimony telluride.

In FIG. 20, it can be seen that the electrodeposited antimony telluridesemiconductor material using the conditions described in Example 5 canbe electrodeposited into the conducting TiN regions to fill the 1-10micron diameter holes on a patterned electrode, and without depositionoccurring on the SiO₂ regions. Referring to FIG. 21, it can be seen fromthe energy dispersive X-ray analysis that after electrodeposition, thispatterned electrode shows peaks corresponding to Sb and Te as well asthe substrate.

From FIGS. 22 and 23 it can be seen that the electrodeposition ofantimony telluride into the micropatterned substrate can be improved byadjusting the relative concentrations of the halometallate salts in theelectrochemical system and by adjusting the potential waveform, leadingto more uniform filling of the TiN regions on the patterned electrode.Referring to FIG. 24, it can be seen from the microfocus X-raydiffraction data that the antimony telluride on the patterned electrodecan be crystallised by annealing at 160° C. for 15 min under N₂ and thatthe diffraction pattern for the material obtained under these conditionsis consistent with Sb₂Te₂.

FIG. 25 shows the cyclic voltammograms obtained using both glassy carbonand TiN electrodes from solutions of each of the halometallate saltsdescribed in Examples 7, 8, 9, 11 and 12, which were used to establishtheir suitability as reagents for electrodeposition of the individualelements. Scanning electron micrographs of the electrodeposited elementsobtained as described in Examples 7, 8, 9, 11 and 12 show the differentmorphologies obtained under the conditions described as shown in FIG.26. It is expected that the morphology and density of theelectrodeposited materials can be altered by varying the potentialwaveforms. With regard to FIG. 27, it can be seen from the energydispersive X-ray analyses that each of the individual elements, indium,antimony, bismuth, selenium and tellurium can be electrodeposited aspure materials from the appropriate halometallate salt, with very littleCl. FIG. 28 shows that the individual elements electrodeposited arecrystalline, and match well with the diffraction patterns from the bulkelements. It is expected that the morphology, purity and density of theelectrodeposited materials can be further optimised by varying thepotential waveforms.

It is highly desirable to be able to deposit germanium from anelectrochemical system. However, germanium is known to be a difficultelement to obtain in this way. This is due to both the tendency toincorporate oxygen into the electrodeposited material, forming germaniumoxide impurities that severely compromise the properties of thesemiconductor, and the sensitivity of many germanium-containing reagentsto water and oxygen. Two halogermanate salts are described, one (Example13) containing germanium(IV) and the other (Example 14) containinggermanium(II). FIG. 29 shows the cyclic voltammogram obtained from aCH₂Cl₂ solution containing [^(n)Bu₄N][GeCl₃] with [^(n)Bu₄N]Cl (Example14), revealing a significant reduction wave at around −1.4 V vs Ag/AgCl(0.1 M Cl⁻, CH₂Cl₂) This is significantly less negative than for thegermanium(IV) reagent described in Example 13, suggesting that the loweroxidation state in Example 14 may be advantageous.

Referring to FIG. 30, it can be seen from the scanning electronmicrograph that electroreduction at a potential at −1.4 V vs Ag/AgCl(0.1 M Cl⁻, CH₂Cl₂) under the conditions described in Example 14, leadsto deposition of a thin film of material on the electrode surface. Theenergy dispersive X-ray analysis of this material shown in FIG. 31 showsthat the only significant elements present are the electrode materialsand a strong peak due to germanium.

X-ray diffraction studies on the material on the electrode surface seenin FIG. 30 shows that germanium is amorphous, However, it can be shownfrom FIG. 32 that the germanium can be crystallised by annealing at 600°C. under N₂, and that the diffraction pattern is consistent withelemental germanium.

FIG. 33 shows the cyclic voltammogram obtained from the electrochemicalsystem containing the three halometallate salts containing germanium,antimony and tellurium. This example was undertaken to establish whetherit would be possible to electrodeposit a ternary germanium antimonytelluride material using the electrochemical system as described inExample 15. It can be seen from FIG. 34 that electrodeposition at −1.75V vs Ag/AgCl (01 M Cl⁻, CH₂Cl₂) for 120 s leads to deposition of theelectrode with almost spherical particles. The energy dispersive X-rayanalysis of this material is shown in FIG. 35, which shows that thedeposited material does contain germanium, antimony and tellurium, withthe only other significant peaks being from the electrode substrate.

X-ray diffraction studies on the material illustrated in FIG. 34 showthat it is amorphous. It can be seen from FIG. 36 that this germaniumantimony telluride material can be crystallised by annealing under N₂ at250° C. for 30 mins.

It can be seen from the scanning electron micrograph shown in FIG. 37that the ternary germanium antimony telluride semiconductor material canbe selectively electrodeposited on the TN regions of a patternedelectrode, allowing pores with 1-3 μm diameter to be filled with theternary alloy.

It is expected that the relative ratios of Ge:Sb:Te on flat electrodesand on patterned electrodes can be adjusted by varying theconcentrations of the halometallate salts in the electrochemical systemand also by varying the potential waveform, as shown for the binaryantimony telluride semiconductor material described in Examples 3 and 4.Further, it is expected that the morphology of the electrodepositedmaterial can be optimised by changing the potential waveform, asdescribed in Example 4 for the antimony telluride material. It can alsobe expected that combining different halometallate salts using thiselectrodeposition method will allow a wide range of other elemental,binary, ternary and doped semiconductor materials to be obtained.

It is to be appreciated that the Examples and drawings have been givenfor the purposes of illustration only and that modifications may bemade. Individual parts of the Examples and drawings are not limited touse in their Examples and drawings, and they may be used in otherExamples and other drawings, and in all aspects of the invention.

1. A process for the electrochemical deposition of a semiconductormaterial, which process comprises: (i) providing a non-aqueous solvent;(ii) providing at least one precursor salt which forms a source of theconstituent elements within the semiconductor material to be deposited;and (iii) electrodepositing the semiconductor material onto an electrodesubstrate using the precursor salt in the non-aqueous solvent,characterised in that: (iv) the semiconductor material is a p-block or apost-transition metal semiconductor material containing at least onep-block element or post-transition metal; and (v) the non-aqueoussolvent is a halocarbon non-aqueous solvent.
 2. A process according toclaim 1 in which the halocarbon non-aqueous solvent is a fluoroalkane, achloroalkane or a bromoalkane.
 3. A process according to claim 1 orclaim 2 in which the halocarbon nonaqueous solvent is dichloromethane,chloroform, difluoromethane, trifluoromethane, 1,1-dichloroethane,1,2-dichloroethane, 1,1,1-trichloroethane or 1,1,2-trichloroethane.
 4. Aprocess according to claim 1 in which the halocarbon non-aqueous solventis a fluoro-, chloro- or bromo-benzene, fluorotoluene or o-, m- orp-fluorotoluene.
 5. A process according to claim 1 in which theprecursor salt is a halometaliate anion salt.
 6. A process according toclaim 5 in which the halometaliate anion is a chlorometallate anion, abromometallate anion, or an iodometallate anion.
 7. A process accordingto claim 6 in which the halometaliate anion salt has the generalformula:[cation]_(x)[M_(z)X_(y)] where x=1, 2 or 3 z=1 and then y=3, 4, 5 or 6z=2 and then y=8, 9 or 10 M=Al, Ga, In, Ge, Sn, Pb, As, Sb, Bi, Se or Teand X=CI, Br or I
 8. A process according to claim 7 in which:[M_(z)X_(y)]= [AlX₄]⁻ [InX₄]⁻ [GeX₅]⁻ [SbX₄]⁻ [BiX₄]⁻ [SbCl₆]⁻ [SeX₆]²⁻[TeX₆]²⁻ [GaX₄]⁻ [GeX6]²⁻ [GeX₃]⁻ [SnX₆]²⁻ [SnX₅]⁻ [SnX₃]⁻ [PbX₃]⁻[PbX₆]²⁻ [AsX₄]⁻ [SbX₅]²⁻ [SbX₆]³⁻ [BiX₅]²⁻ [BiX₆]³⁻ [Sb₂X₈]²⁻ [Bi₂X₈]²⁻[Se₂X₁₀]²⁻ [Te₂X₁₀]²⁻ [CdX₄]²⁻ [CdX₅]³⁻ [HgX₄]²⁻ [HgX₅]²⁻ [HgX₃]⁻
 9. Aprocess according to claim 1 in which the precursor salt contains aredox inactive cation.
 10. A process according to claim 9 in which theredox inactive cation in the precursor salt is a quaternary ammoniumcation having a group [R4N]⁺ where R=alkyl.
 11. (canceled)
 12. A processaccording to claim 9 in which the redox inactive cation in the precursorsalt is imidazolium; alkyl substituted imidazolium, where alkyl ismethyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, cyclopentyl,cyclohexyl, or mixtures thereof; pyrrolidinium; alkyl substitutedpyrrolidinium where alkyl is methyl, ethyl, propyl, butyl, pentyl,hexyl, benzyl, cyclopentyl, cyclohexyl, or mixtures thereof; [PPh₄]⁺;[AsPh₄]⁺ or [(PPh₃)₂N]⁺.
 13. A process according to claim 1 andincluding providing a supporting electrolyte salt for the non-aqueoussolvent.
 14. A process according to claim 13 in which the supportingelectrolyte salt is a redox inactive salt.
 15. A process according toclaim 14 in which the redox inactive salt is in the form of a cation andan anion.
 16. A process according to claim 13 in which the anion in thesupporting electrolyte salt is halide, tetrafluoroborate,hexafluorophosphate, a tetra-arylborate, a fluorinated tetra-arylborate,tetra-alkoxyaluminate, or a fluorinated tetra-alkoxyaluminate anion. 17.A process according to claim 13 in which the cation in the supportingelectrolyte salt is a redox inactive quaternary ammonium cation salthaving a group [R₄N]⁺ where R=alkyl.
 18. (canceled)
 19. A processaccording to claim 1 in which the electrodeposition is a continuouselectrodeposition. 20.-21. (canceled)
 22. A process according to claim 1in which the electrode substrate is an electrode substrate havinginsulating pores, in which the semiconductor material is deposited as ashaped structure, in which the shaped structure is a plurality ofpillars, and in which the pillars are electrodeposited in the insulatingpores.
 23. A process according to claim 1 in which the semiconductormaterial is electrodeposited all over the electrode substrate, theelectrode substrate being a flat electrode substrate.
 24. A processaccording to claim 1 in which the semiconductor material is a compoundsemiconductor containing two or more p-block elements, a singlesemiconductor element or a semiconductor alloy.